This invention relates generally to medical devices for delivering therapeutic agents to selected tissue site through a hydrophilic membrane. More particularly the invention relates to catheter systems that have injection ports for delivery of therapeutic fluids and a membrane attached to a distal portion of the catheter into which the fluid is delivered, thereby inflating the balloon. The membrane is formed from a hydrophilic polymer that exhibits a predetermined permeability such that therapeutic solutions delivered through the injection port(s) into the membrane are contacted directly, which are in contact with the inflated membrane.
Various forms of drug delivery catheters are known in the art. They generally comprise an elongated flexible catheter body having an inflatable member at a distal end portion thereof where the inflatable member or xe2x80x9cballoonxe2x80x9d has pores formed in the wall thereof through which a drug containing fluid can profuse. For example, U.S. Pat. No. 5,709,653 to Leone uses a balloon catheter with a porous balloon for allowing a photodynamic treatment fluid to pass through the pores and infuse into the wall of a body vessel in which the catheter is disposed. Other patents utilizing a porous balloon for drug delivery include Racchini et al. U.S. Pat. No. 5,458,568; Sahatjian et al. U.S. Pat. No. 5,674,192 and Shapland et al. U.S. Pat. No. 5,628,730.
Unfortunately, porous balloons are difficult to manufacture (requiring precision drilling of an elastic material) and the minimum practical pore size is often much larger than desired. Moreover, the typical porous balloon system of the prior art has an undesirable release profile, characterized by rapid initial release of a drug or other agent followed by an exponential drop-off as the balloon deflates and the fluid pressure driving the agent through the pores becomes smaller and smaller.
Accordingly, there exists a need for better drug delivery systems and, in particular, delivery systems with greater control over release rates. Balloon or other membrane-based drug delivery systems that can selectively pass molecules at a controlled and reproducible rate would satisfy a long-felt need in the art.
The present invention circumvents the problems described above by delivering a therapeutic agent, e.g., a medicament, into an area in need thereof, via a membrane that permits greater control of the application and release rates of the medicament. In a particular embodiment, the invention provides a device, which allows chemotherapeutic or radiosensitized treatment of a particular diseased tissue area with minimal if any exposure of non-diseased tissue to the treatment. Drug delivery vehicles and catheter systems of the invention are disclosed for controlled release of therapeutic agents, e.g., medicaments such as chemotherapeutic agents or radiosensitizers, employing a permeable hydrogel matrix, e.g., a membrane, and a reservoir for an inflation fluid carrying a therapeutic agent.
The devices of the present invention can be used in conjunction with a catheter or similar instrument having an elongated hollow body member and a lumen extending therethrough to permit fluid communication between a proximal infusion port and a permeable membrane disposed at the distal end of the catheter body. The device preferably comprises an expandable, hydrophilic polymer membrane, e.g., a hydrogel membrane, e.g., a balloon, having a predetermined permeability with respect to an inflation fluid. One preferred hydrophilic polymer is a hydrogel capable of imbibing an aqueous solution to reach a state in which it comprises between 50% and 98% water by weight in equilibrium. In this state, the hydrogel membrane serves to control the rate of medicament delivery.
By injecting an inflation fluid comprising an aqueous solution containing a medicament, the membrane member can be inflated to engage body tissue (e.g., the interior surface of a blood vessel or other body lumen or tissue surrounding a natural or excised interstitial space within the body). The membrane can engage the body tissue over a substantial portion of its length and simultaneously exude the inflation fluid containing the medicament through the membrane so as to bathe the engaged tissue and surrounding tissues, e.g., a vessel wall, with the drug or other therapeutic substance.
The invention is also drawn to methods for treating aberrant cells or cancer in a body cavity. The methods include inserting a catheter including an elongated tubular body member into a body cavity, the tubular body having a proximal end, a distal end and a lumen extending therebetween, with an inflation port extending through a wall of the tubular body member in fluid communication with the lumen. An expandable membrane member is affixed to the catheter body member near the distal end and in fluid communication with at least one inflation port.
The membrane member includes a hydrophilic polymer having a predetermined permeability to migration of inflation fluid therethrough. An inflation solution containing a medicament is injected into the expandable membrane such that the medicament permeates through the membrane over a period of time treating the aberrant.
In one embodiment, the method further includes slidably positioning an insertion tube with radioactive pellet(s), e.g., seed(s), into a lumen of the catheter, such that ionizing radiation strikes the medicament, preferably a chemotherapeutic agent or a radiosensitizer, thereby treating the aberrant cells with an activated medicament.
In another embodiment, the methods include inflating a second membrane, which is fixedly attached to the catheter and proximate to the first membrane with a solution containing a radioactive isotope. Preferably, the radioactive solution emits ionizing radiation that interacts with a chemotherapeutic agent or a radiosensitizer forming activated molecules useful for treating aberrant cells or cancer.
The invention will next be described in connection with illustrated embodiments. However, it should be clear that various additions, subtractions and substitutions can be made without departing from the spirit or scope of the invention. For example, the membranes of the present invention can be bonded to the catheter in many different ways so long as a fluid pathway exists between an inflation fluid source and the membrane. The membrane can be multi-walled or multi-layered so long as the overall structure has a predefined permeability.
The membrane can be affixed or otherwise joined to the catheter body without the need for defined inflation ports and can also be stored in a collapsed or recessed state prior to use, e.g., an open-ended catheter. The membrane and catheter components can be sold separately and permeable membranes according to the invention can be designed or adapted to connect to various conventional medical instruments. Broadly, the invention encompasses each of the various elements, methods and features described herein alone or in combination with any other element, method or feature.